Southern Derbyshire Shared Care Pathology Guidelines. Hypocalcaemia in Adults

Transcription

1 Southern Derbyshire Shared Care Pathology Guidelines Hypocalcaemia in Adults Purpose of Guideline The investigation and management of patients with newly diagnosed hypocalcaemia Definition Adjusted (corrected) calcium <2.20 mmol/l Corrected or Adjusted Calcium We report total calcium and corrected (adjusted for albumin) calcium results. All the calcium values in this guideline refer to the corrected values. This adjustment is only an approximation. The correction is not valid in acid-base disorders. For example although the corrected calcium may be normal in acute respiratory alkalosis, the ionised calcium may be low, and the patient may have symptoms of hypocalcaemia, such as parasthesia. When is hypocalcaemia considered a medical emergency? Adjusted Calcium mmol/l Not a medical emergency Adjusted Calcium mmol/l Possible medical emergency Adjusted Calcium <1.80 mmol/l Usually a medical emergency These limits are for guidance only; the severity of the patient s symptoms, and other factors, e.g. rapidity of the fall in calcium, renal function, will also determine whether the patient requires emergency admission. The laboratory will telephone all calcium results <2.00 mmol/l, Monday to Friday when GP practices are open. Calcium results <1.80 mmol/l will usually be telephoned to Derbyshire Health United when the GP practice is closed. When is hypocalcaemia suspected? Mild hypocalcaemia is not uncommon, and in many patients the only symptoms may be vague muscular aches and pains. Obviously the number and severity of symptoms will be dependent on the degree of hypocalcaemia. Severe symptoms such as tetany are rare, but parasthesia can be seen. Cardiovascular complications, arrhythmias, hypotension and heart failure can all be seen. Patients are at risk of hypocalcaemia if they have actual or functional Vitamin D deficiency. Authorised by Julia Forsyth Page 1 of 5

2 What are the causes of hypocalcaemia? Actual Vitamin D Deficiency o Dietary o Lack of Sunlight o Malabsorption, especially pancreatic disease and coeliac disease Functional Vitamin D Deficiency o Renal Disease (lack of 1-Hydroxylation) o Liver Disease (lack of 25-Hydroxylation) Magnesium deficiency Hypoparathyroidism o Autoimmune o Post Surgery What happens next? Adjusted Calcium <1.80 mmol/l (± symptoms) or <2.00 mmol/l (+ symptoms) The majority of patients need urgent referral to hospital, especially if symptomatic and/or if they have other co-morbidities. Adjusted Calcium mmol/l without symptoms If asymptomatic, immediate referral is not required. For patients presenting with hypocalcaemia without a known cause, dependent upon clinical details provided the laboratory measures: PTH Magnesium U & E Vitamin D Appropriate actions based on these results are shown in the flow chart below. Authorised by Julia Forsyth Page 2 of 5

3 Investigating New Hypocalcaemia Adjusted Calcium <1.80 mmol/l (± symptoms) or <2.0 mmol/l (+ symptoms) Urgent referral to hospital indicated Adjusted Calcium mmol/l (without symptoms) Immediate referral not indicated Measure PTH, Mg, U&E, Vitamin D Is PTH high? (> 65ng/L) No Check Vit D level Vitamin D deficiency very likely Check Vit D level Vit D deficiency alone is an unlikely cause of hypocalcaemia but suggest high dose replacement for completeness if Vitamin D <30 nmol/l: (100,000 units first day and then 20,000 units daily up to total dose of 300,000 units) Vitamin D <30 nmol/l High dose replacement required: 100,000 units first day and then 20,000 units daily up to total dose of 300,000 units If PTH not raised it is important to check for Mg deficiency, whatever the Vitamin D level Is Mg low? (< 0.70 mmol/l) No Magnesium Deficiency (PTH typically normal) Refer to Shared Care Hypomagnesaemia guideline Mg mmol/l oral replacement Mg <0.4 mmol/l i.v. replacement, i.e. admit patient same day or discuss with endocrinologist Is PTH low or low-normal? Hypocalcaemia with low / low-normal PTH and normal Mg suggests hypoparathyroidism. It is not common and can arise from autoimmune disease, infiltration, post-surgery and congenital causes. All newly diagnosed hypoparathyroidism should be referred to a Consultant Endocrinologist for full assessment and management plan Authorised by Julia Forsyth Page 3 of 5

4 Hypocalcaemia with raised PTH (>65 ng/l) Vitamin D deficiency is the usual diagnosis of hypocalcaemia with raised PTH. If the patient s renal function is normal the patient can present with a low serum phosphate (<0.8 mmol/l). The measurement of vitamin D itself is advised and treatment can commence straight away (please refer to Vitamin D guideline on the Shared Care Pathology Website). If renal, gastrointestinal or hepatic involvement is present the appropriate referral should be made when required. Hypocalcaemia with normal or decreased PTH (<65 ng/l) In patients with low serum calcium and a PTH within the reference range it is important to rule out magnesium deficiency, which gives rise to a blunted PTH response. Magnesium deficiency often requires correction to enable the calcium to be normalised (please refer to the hypomagnesaemia guideline on the Shared Care Pathology Website). In patients with low serum calcium, a PTH below the reference range is virtually diagnostic for hypoparathyroidism. Causes of Magnesium Deficiency Renal Loss Diuretics, especially Loop Diuretics Cytotoxic Drugs Aminoglycosides Immunosuppressants Miscellaneous drugs, e.g. PPI s, Bisphosphonates GI Severe Diarrhoea Malnutrition Alcoholism What Next? In patients at high risk of vitamin D deficiency (housebound, elderly, south Asian) with normal renal function and appropriately elevated PTH, treat with replacement doses of vitamin D and ensure adequate calcium is provided (see vitamin D guidelines). Otherwise, patients should be referred to an outpatient clinic depending on the initial assessment, for further investigation for an underlying cause and initiation of treatment. This may include correction of the underlying cause, calcium, vitamin D or vitamin D analogues. If renal impairment (CKD 3 or worse) refer to renal team If features of malabsorption refer to GI Otherwise refer to endocrinology Magnesium Deficiency: see separate guideline Vitamin D Deficiency: see separate guideline Authorised by Julia Forsyth Page 4 of 5

5 Contacts Duty Biochemist (8am to 7pm, Mon Fri) On Call Consultant Biochemist Via RDH switchboard, (24/7) Endocrinology Advice (9am 5pm, Mon Fri) Renal Registrar (9am to 9pm) via RDH switchboard bleep 8121 MAU and ACC OR MAU Nurse in Charge Authors: Rustam Rea, Roger Stanworth, Paul Masters, Nigel Lawson November 2011 Reviewed by: Date: Expiry date: Dr P Blackwell, Mrs H Seddon Nov th Nov 2015 Dr R Stanworth, Dr P Masters, Dr Mar st Mar 2018 P Blackwell, Mrs H Seddon Dr R Stanworth, Dr P Blackwell, Mrs H Seddon May st May 2020 Authorised by Julia Forsyth Page 5 of 5